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Glial Fibrillary Acidic Protein (GFAP) is an intermediate filament protein expressed in the central nervous system (CNS) particularly by astrocytes. It plays diverse roles in CNS physiology and pathology. Recently, a CNS inflammatory encephalitis related to GFAP autoimmunity was described. Patients with GFAP autoimmune astrocytopathy with GFAP-IgG as a biomarker develop meningoencephalomyelitis with inflammation of the meninges, brain, and spinal cord. Rarely, there is ophthalmological involvement. The disease may be accompanied by neoplasms.

Recently, positive neuronal intermediate filaments (NIF) IgG staining was found to exist in patients with paraneoplastic neurological disorders, suggesting a strong association with malignancy, particularly those of neuroendocrine lineage.

While both GFAP and NIF autoimmune neurological disorders have been associated with neoplasms, NIF IgG positivity has not been reported in the setting of GFAP meningoencephalomyelitis. Here, we report a novel case of NIF IgG positivity in a patient with GFAP astrocyopathy.

A 48-year-old lady presented initially with optic disc inflammation. Comprehensive examination and investigation revealed radiological and clinical findings consistent with GFAP astrocytopathy. These included bilateral optic disc swelling, seizures, myelopathy, and diffuse cerebral FLAIR hyperintensities with enhancement in the deep white matter exhibiting a radial distribution. She was treated with high dose steroids and immunosuppressants with resulting clinical stability. Her Cerebrospinal Fluid (CSF) tested positive for GFAP antibody, and an NIF-IgG staining pattern was found. Subsequent cell-based assay performed to determine NIF-IgG profile was positive for all three of Alpha-Internexin IgG, Neurofilament Light Chain IgG, and Neurofilament Heavy Chain IgG. Further comprehensive imaging has yet to reveal a primary neoplasm, for which she remains under close follow up.

This case illustrates the possibility of the co-existence of GFAP and NIF antibody positivity. In light of overlapping clinical features in particular the potential presence of neoplasms, it highlights the importance of surveillance for malignancy.